Hi. It is probably a very dumb question, but for me it is hard to understand.

I always read tha resistors reduce the current but not the voltage. I understand that they reduce the current, that is clear. But I also think the voltage across the load, provided that load works in acordance with ohms law. In that scenario, Can I say that putting a resistor in series is the same as reducing the voltage of the power supply?

Thank you

Best regards

 

If the circuit draws a constant current, yes, the resistor is equivalent to dropping the voltage just enough to get that current. The extra voltage appears across the resistor.

But if the current drawn is variable, the situation is different. At low current, the resistor will drop very little voltage, and at high current perhaps too much. Thus the voltage supplied to the load is varying. This is why we use voltage regulators, which basically change the resistance to keep the desired voltage on the load.

 

Hello,

The resistor will create a voltage drop depending on the current.
When the current varies, the voltage drop will vary.
An example of creating a voltage drop is the series resistor for a led.
The value of this resistor can be calculated as followed:
R = (Vsupply - Vled) / Iled.
In case of a supply voltage of 6 Volts and a led voltage of 3 Volts, with a led current of 20 mA, the result will be:
( 6 - 3 Volts ) / 0.02 Amp = 150 Ohms.

Bertus